5.2. The Assignment Operator

We've already used the
assignment operator frequently. It can place a value into a variable,
array element, or object property. Assignment operations take the
form:

identifier = expression

The
identifier is the variable, array element, or
object property into which we want to place our value. The
expression represents the value (i.e.,
data) that we want to store. For example:

x = 4; // Assign 4 to the variable x
x = y; // Assign the value of y to the variable x
name = "dj duong"; // Assign a string to the variable name
products[3] = "Flash"; // Assign a string to the 4th element of products
// Assign a number to the area property of square
square.area = square.width * 2;

We may also perform multiple assignment operations at once, like this:

x = y = 4; // Set both x and y to 4

Remember that assignment operations have right-to-left associativity,
so 4 is assigned first to y then the value of
y (which is now 4) is assigned to
x.

5.2.1. Combining Operations with Assignment

Assignment operations are often used to set a variable's new
value based in part on its old value. For example:

ActionScript supports a shorthand version of assignment, called
compound assignment that combines operators such as +,
-, / with the assignment operator to form a single
"calculate-while-assigning" operation. So, to combine
addition with assignment we use +=. To combine division with
assignment, we use /=. The previous examples, hence, can be written
more succinctly with compound assignment operators as follows: